The present invention relates to apparatus and methods for inserting an intraocular lens through a small incision into an eye. More particularly, the invention relates to such apparatus and methods utilizing a plunger to displace an intraocular lens through a tubular insertion apparatus, wherein the intraocular lens is reliably and safely engaged by the plunger.
An intraocular lens (IOL) is implanted in the eye, for example, as a replacement for the natural crystalline lens after cataract surgery or to alter the optical properties of (provide vision correction to) an eye in which the natural lens remains. IOLs often include an optic, and preferably at least one flexible fixation member or haptic, which extends from the optic and becomes affixed in the eye to secure the lens in position. The optic normally includes an optically clear lens. Implantation of such IOLs into the eye often involves making an incision in the eye. Making the incision as small as possible reduces trauma and speeds healing.
IOLs are known which are foldable (deformable) so that the IOL can be inserted into the eye through an incision smaller than the diameter of the lens.
Some of the most generally accepted insertion apparatus employ a hollow insertion tube having a diameter which permits the folded IOL to pass freely through the tube without permanent deformation, and without causing the surgeon to apply excessive force to overcome friction between the walls of the insertion tube and the IOL. Excessive force can result in the premature ejection of the IOL before the surgeon is ready to position it within the patient""s eye. It would be advantageous to provide IOL insertion apparatus and methods which facilitate the passage of a folded IOL through the apparatus and the insertion of the IOL in the eye in easy, effective and controlled manner while avoiding damage to the IOL and undue trauma to the patient.
A very useful technique for inserting an IOL into the eye includes the use of an IOL injector or cartridge, such as the IOL injector described in Bartell, U.S. Pat. No. 4,681,102, and also in Brady, U.S. Pat. No. 5,702,402. These IOL injectors include a load chamber which is connected to an injection tube. The load chamber includes a lumen for receiving the IOL and is hinged so that the side walls thereof can be opened like a book. Closure of this lumen folds the IOL and maintains the IOL in a folded state. The injection tube includes a small diameter distal tip which is insertable into the incision within the eye. The cartridge is held in a handpiece which is coupled to a plunger rod. The plunger rod moves distally through the load chamber and injection tube to urge the IOL to pass through the tube and into the eye. The IOL is thus transferred from the load chamber through the injection tube and into the eye. As the IOL moves from the load chamber distally though the injection tube, its folded configuration is further compressed by a narrowing of the injection lumen. These IOL injectors simplify the placement of the IOL within the eye and reduce chances of surgeon error.
Although the IOL can pass freely through the injection tube, it must first be secured by the engaging end of the plunger rod. Because the plunger rod extends fully through the cartridge, its engaging end must be sized small enough to pass through the narrowest lumen of the cartridge, at the distal end of the injection tube. At the same time, the load chamber is relatively larger than the injection lumen so that the surgeon can easily place the IOL therein for folding. Therefore, there is a relatively large space surrounding the plunger rod engaging end as it enters the load chamber. Additionally, most plunger rods are not rigidly guided along an axis, but are relatively loosely coupled to a drive mechanism so that there is some radial play at the engaging end. Moreover, the IOL and cartridge are made of materials that interact to produce a coefficient of friction therebetween that must be overcome when urging the IOL through the tube, even with the introduction of a lubricating medium. The loose fit of the plunger rod in the load chamber in conjunction with the friction between the IOL and cartridge often causes the plunger rod to fail to engage the proximal edge of the IOL. That is, unless the plunger rod squarely contacts the proximal edge of the IOL, it may miss completely or deform the edge and ride up over the IOL, with the end result that the IOL remains in place while the plunger rod passes therethrough.
An intraocular lens insertion apparatus that attempts to address this problem is disclosed in Brown, et al., U.S. Pat. No. 6,010,510, and includes an injector plunger having a blunt, rounded tip offset from the centerline of the plunger rod. The offset tip assures that the tip is biased downward against the bottom of the cartridge bore to help ensure proper engagement of the intraocular lens therein. However, there is still a possibility that the plunger tip might ride underneath or otherwise fail to engage the intraocular lens.
There is thus a need for a more effective and safe means for engaging and displacing an intraocular lens from within an insertion apparatus.
The present invention provides an improved apparatus for inserting an intraocular lens through an incision into an eye. The apparatus operates in an environment that is similar to existing systems, with a cartridge being loaded into a handpiece, and plunger rod of the handpiece extending through a lumen in the cartridge to push an intraocular lens from an injection tube of the cartridge through an incision in the eye. The apparatus of the present invention provides structure within the cartridge and on the plunger rod that ensures positive engagement between the plunger rod and the intraocular lens to more reliably advance the intraocular lens into the eye in the desired orientation.
In one particular embodiment, the present invention provides an intraocular lens insertion apparatus including a cartridge having a longitudinal lumen extending through an injection tube and terminating in a mouth on a distal end thereof. An intraocular lens chamber sized to contain an intraocular lens is defined on a proximal end of the cartridge and forms part of the lumen. The intraocular lens has a proximal edge and a distal edge with respect to the cartridge, and at least a portion of the chamber is configured with a non-circular cross-section such that, with the intraocular lens positioned therein, a space along one wall is created adjacent to the proximal edge of the lens. The apparatus further includes a housing adapted to hold the cartridge and having a lumen generally aligned with the cartridge lumen. A plunger rod having an engaging head is provided that can be linearly displaced along the housing lumen into the cartridge lumen with a distal lip of the engaging head aligned with the space. Displacement of the plunger rod in a distal direction causes the distal lip to enter the space adjacent the proximal edge of the intraocular lens such that the engaging head reliably engages the intraocular lens. In a preferred embodiment, the chamber opens at a hinge so that the intraocular lens can be folded therein. Also, the engaging head of the plunger rod may have a forked end defined by the distal lip and another lip spaced therefrom, with a groove formed therebetween for capturing the proximal edge of the intraocular lens. The space may be created by a recess in one wall of the cartridge, the recess being formed only at the proximal end of the cartridge or extending longitudinally in a channel. Alternatively, a raised area in one wall of the cartridge is provided with the proximal edge of the lens being elevated above the wall to create the space.
In another aspect of the invention, an intraocular lens insertion apparatus comprises a cartridge for receiving an intraocular lens in a proximal chamber. The cartridge defines a distal injection tube having a lumen in communication with the chamber along a common axis. The chamber further includes a generally tubular wall and being configured such that, with the intraocular lens positioned therein, a space along the wall is created adjacent to a proximal edge of the lens. The apparatus also includes a handpiece for mounting the cartridge and having a plunger rod adapted to be displaced generally along the axis. The plunger rod includes a bifurcated distal end with a pair of lips separated by a groove and sized to receive a proximal edge of the intraocular lens. One lip of the plunger rod aligns with the space such that displacement of the plunger rod reliably captures the proximal edge of an intraocular lens within the groove. The space may be created by a recess in the wall of the cartridge, the recess being formed only at the proximal end of the cartridge or extending longitudinally in a channel. Alternatively, a raised area in the wall of the cartridge is provided with the proximal edge of the lens being elevated above the wall to create the space. Desirably, the lumen converges from the chamber distally through the injection tube such that an intraocular lens is compressed in size upon passage therethrough. The plunger rod may define an engaging head on a distal end with a flattened oval-shaped body and an axially-extending projection on one wide side that terminates in the lip aligned with the space. Optionally, the cartridge may include an axially extending wall portion projecting inwardly to the chamber opposite the wall to help guide the distal end of the plunger rod such that the one lip extends into the space.
Another aspect of the invention is a method of inserting an intraocular lens into an eye including providing a cartridge, a housing, and plunger rod. The cartridge has a chamber for receiving an intraocular lens and a delivery lumen defining an axis and extending distally therefrom through an insertion tube. The cartridge mounts in the housing, and the plunger rod axially slides within housing and completely through the cartridge. The plunger rod has an engaging head on its distal end with an axially extending lip. The method includes placing an intraocular lens within the cartridge, the chamber being configured such that a space is created adjacent a proximal edge of an intraocular lens positioned therein. The method further includes mounting the cartridge in the housing with the plunger rod retracted in a proximal direction, positioning the insertion tube within the eye, and axially advancing the plunger rod in a distal direction. First, the lip on the plunger rod enters the space prior to contact between the engaging head and the proximal edge of intraocular lens. Further advancement of the plunger rod causes the engaging head to contact the proximal edge of the intraocular lens. Full advancement of the plunger rod expels the intraocular lens from the delivery lumen into the eye. Desirably, the chamber opens at a hinge and the method includes placing an unfolded intraocular lens in the open chamber and folding the intraocular lens by closing the chamber. Also, the chamber may be larger than the delivery lumen such that intraocular lens is compressed in size upon passage from the chamber to the delivery lumen. Finally, the cartridge may include an axially-extending wall portion directed into the chamber, wherein the method includes guiding the lip into the space upon contact of the distal end of the plunger rod with the wall portion.
In another method, an intraocular lens is positioned within a cartridge chamber such that a proximal edge of the lens extends beyond a proximal end of the cartridge. A plunger rod having a bifurcated engagement head is distally advanced such that the proximal edge of the lens is captured in a groove of the engagement head prior to entry of the plunger rod into the cartridge chamber. The captured lens is then urged through the chamber and from the injection tube into a patient""s eye.
These and other aspects of the present invention will become apparent in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.